function rolloverImage() {
	if (!document.getElementsByTagName) return false;
	var img = document.getElementsByTagName('img');
	for (var i = 0, l = img.length; i < l; i++) {
		var imgList = img[i];
		if (imgList.getAttribute('src').match(/_off\./)) {
			imgList.offSrc = imgList.getAttribute('src');
			imgList.ext = imgList.offSrc.substring(imgList.offSrc.lastIndexOf('.'), imgList.offSrc.length);
			imgList.onSrc = imgList.offSrc.replace('_off' + imgList.ext, imgList.ext);

			var preload = new Array();
			preload[i] = new Image();
			preload[i].setAttribute('src', imgList.onSrc);

			imgList.onmouseover = function() {
				this.setAttribute('src', this.onSrc);
			}
			imgList.onmouseout = function() {
				this.setAttribute('src', this.offSrc);
			}
		}
	}
}

function addEvent(elm, listener, fn) {
	try {
		elm.addEventListener(listener, fn, false);
	} catch(e) {
		elm.attachEvent('on' + listener, fn);
	}
}

addEvent(window, 'load', rolloverImage);